Electric heater.



5 tady, and State of 4 a receptacle embodying my invention.

'-13 5 throughout with insulating material.

4o drical surface is wound 45 an iron JOHANNES HARDN, or

SCHENECTADY, NEW YORK, ASSIGNOR TO GEN- ERAL ELECTRIC COMPANY, ACORPORATION OF NEW YORK.

ELECTRIC HEATER.

Specification of Letters Iatexitiiii) Patented May 1, 190e.'

Application filed March 27, 1905. Serial N0. 252,173.

To all whom, it 11m/y concern/f Be it known that I, JOHANNES HARDN, asubject of the King of Sweden and Norway, residing in Schenectady,county of Schenec- New York, have invented certain new and usefulImprovements in Electric Heaters, of which the following is aspecification.

This invention relates to electric heaters,

1o and has for its object the provision of a heater of such a characterthat it maybe operated efficiently by either a direct or an alternatingcurrent.

Further objects are the provision of im- 15 proved means forcompensating for the rapid increase of resistance with the rise ofternperature in iron or other resistance-conductors and producingdifferent heats by varying the relative arrangement of the resist- 2 0SJICGS.

My invention further consists in the details of construction and thecombination of elements hereinafter described, and particularly setforth in the claims annexed to and form- 2 5 ing a part of thisspecification.

1 is an elevation of Fig. 2 is an enlarged sectional view of the same.Fig. 3 is a diagram of the circuits employed,

In the drawings, Figure 3o showing the windings arranged in parallel,

and Fig. 4 1s a similar view showing the in s arranged in series.

eferring to the drawings, 1 is a metallic vessel of a suitable shapepreferably corered prefer to use an iron vessel coated with enamel 2,vessels of enamel-ware being very well known in the art. The shape ofthe vessel is preferably cylindrical, and upon the cylinresistance-wire,either of iron or German silver or any of the wellknownresistance-conductors. I have shown this resistance as comprising twoseparate windings 3 and 4, each winding composed of .ribbon woundilatwise. The windings ai c separated from each other by a strip ofinsulating material 5, the contact-rings 6 and 7 serving as terminals ofthe said windings. A layer of cementisnow formed over wind- 50 andaround the wires, the cement preferably or other plastic heat-resistingterial will be satisfactory. The cement 1s now heated until the gasesare driven off and it is caused to harden. A porous asbestos cover orcasing 9 is now placed over the cement, so as to entirely inclose thewinding.

It has been found that the resistance-conductor has 'a low initialresistance which increases so rapidly with the increase-of temperaturethat a large amount of current is taken at first; but as the temperaturerises it is cut down considerably. In order to compensate for ithis andalso in order to have some heat generatedin the bottom of the vessel, amass of powder preferably containing iron-filings and silicon is placedadjacent the bottom of the receptacle. This mixture has an oppositeresistance temperature coefficient to that of iron, and a compensatingeffect is thereby obtained. The powder has a high initial resistancewhich comes down when it heated, which is the reverse of the actiontaking place in the case of the iron wire.

I have divided the powder into two layer: 1() and 11, separated by ametallic plate 1i and having similar plates 13 on opposit sides of andin contact with the layers These plates are primarily for the urpose omaking a good contact between t e powde and the wires. As shown in thedrawings the two outside plates 13 are each connecte with one end of thewindings 3 and 4 b means of con `cts 13 and 13, the other en of eachwinding being connected with tl: terminals 14 15 through contacts 14 and15 The central plate 12 is connected With ai other terminal 16.. At 17 Ihave shown connector-plug having three sockets, wij which the terminals14, 15, and 16 are adap ed to engage. These terminals are arrange in ametallic casing or cover 17', which su rounds the winding and isseparated fro the asbestos sheet by a small air-space.

Referring to Fig. 3, it ywill be seen th when the connector 17 is in theposition which the three terminals engage the thi sockets the directionof the current is as f lows: from lead 18 through terminal 16, w 19,thence through the two layers 10 and and windings 3 and 4 in parallelback to 1 terminals 14 15 and lead 20. By shifting connector 17 so thatonly the terminals 14 are in engagement with the sockets, as shoinsulating mai in Fig. 4, the directionv of the current will be asfollows: from lead 18 through terminal 15, winding 3, lower plate 13,layers 10 and 11 in series, winding 4, and terminal 14 to lead 20. Bythis arrangement oi' windings two diierent heats may be given to thereceptacle by simply reversing the connector. It will thus be seen thatI have provided a heater which may be used efliciently with either adirect or an alternating current. I have found that good results havebeen obtained by so arranging the turns of the resistance-conductor thatabout eighty per cent. of the heat is generated by the ohmic resistanceand about twenty per cent. is generated by the transform er effect.These proportions, however, may be varied somewhat to suit conditions.

What I claim as new, and desire to secure by Letters Patent of the.United States, is-

1. An electric heater, comprising a receptacle, and a resistance forheating the same, one portion of which has a positive and the other anegative resistance temperature coei'licient, both portions being inheat-conductive relation with said receptacle.

2. An electric heater, comprising a receptacle, an electric conductor(the resistance of which varies directly as the temperature) 'woundaround the same, and another conductor in circuit therewith and inheat-conductive relation with said receptacle, the resistance of whichvaries inversely as the temperature.

3. An electric heater, comprising a receptacle, a resistance-conductorwound thereon, and a granular resistance in heat-conductive relationwith said receptacle and in circuit with said resistance-conductor.

4. In an electric heater, the combination of an enameled receptacle, aresistance-conductor thereon, and a powdered resistance of negativetemperature coefficient in heatconductive relation with said receptacleand in circuit with said resistance-conductor.

5. In an electric heater, the combination of a receptacle, a pluralityof resistances in heat-conductive relation therewith, each comprising aconductor, one portion of which has a positive and the other a negativeresistance temperature coefiicient, and means whereby the relativearrangement of said conductors may be varied.

6. In an electric heater, the combination of a receptacle, a pluralityof resistances in heat-conductive relation therewith, each of whichcomprises a resistance-wire having a positive temperature coelicient anda granular resistance having a negative coeflicient, and means wherebyeither a series or parallel arrangement or' said conductors may beeffected.

7. In an electric heater, the combination of an enameled metallicreceptacle of good magnetic permeability, a plurality ofresistance-conductors having a positive temperature coeflicient woundupon said enamel, granular resistances having a negative temperaturecoe'licient in circuit with said conductors and in heat-conductiverelation with said receptacle, and means whereby either a series orparallel arrangement of said conductors may be effected.

S. In an electric heater, the combination of an insulated ironreceptacle, a resistanceconductor wound thereon, a coating of plasticmaterial surrounding said winding, a casing surrounding the same butseparated therefrom, and a granular 'resistance in circuit with saidconductor and adjacent the bottom of said receptacle.

9. In an electric heater, the combination of an insulated metallicreceptacle, resistance-conductors wound thereon, layers of powderedresistance containing iron -lings in he'at-conductive relation with thebottom of said receptacle and in circuit with said conductors, and meansfor varying the direction of a current through said resistances.

10. In an electric heater, the combination of an enameled metallicreceptacle, a resistance-conductor wound thereon, and a layer ofpowdered resistance containing iron-filings and silicon in circuit withsaid conductor and in heat-conductive relation with the bottom of saidreceptacle.

11. An electric heater comprising a receptacle of good magneticpermeability, a conductor arranged in inductive relation thereto, anohmic heating-resistance in series with said conductor and inheat-conductive relation with said receptacle whereby the latter may beheated by both a transformer and ohmic effect.

In witness whereof I have hereunto set my hand this 23d day of March,1905, d

JOHANNES HARDEN.

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD.

